If you want to get to know someone better, you approach them and talk to them, get to actually know them better; liking/disliking isn't a thought process, you can't "decide" you like someone or they like you, it's an actual process based on in-person experience with the other and knowing yourself and what you like and dislike. If you feel good when you are actually around that person, you want to be with that person, want that person as a friend. If you are uncomfortable around a person, do not want to be around that person feeling those feelings, then you do not have that person as a friend.

Once you get to know a person a bit, see that you make one another feel good and enjoy each other's company then you can take it to the next step, see if you would enjoy a deeper, more intimate relationship with each other. But it is always a two-person job, it's the actual interaction and communication which is important, not what one thinks is going on. What we think needs checking with reality, especially if it is about another person. Only another person can tell us what they think and feel.